The present invention relates generally to connection discovery in optical networks and, more particularly, to a method and apparatus for determining the existence of connections established between a set of optical amplifiers and a processing device. The present invention also pertains to determining the existence of connections established between an optical amplifier and a mid-stage access (MSA) device.
Optical devices such as spectrum analyzers, cross-connects, switches, dynamic gain flattening filters (DGFFs) and multiplexers are adapted to process optical signals received from various sources. In many cases, the optical signals are amplified by optical amplifiers prior to their arrival at the input ports of the device. The physical interconnection pattern between the optical amplifiers and the input ports of the device defines a xe2x80x9cconnection mapxe2x80x9d. Accurate knowledge of the connection map is necessary for the processing device to successfully execute its intended function such as spectral analysis, switching, filtering or multiplexing.
Knowledge of the connection map can be gained by manually inspecting the connection existing between each amplifier and the processing device. However, this is a laborious process that is prone to human error and can result in hazardous exposure if a given optical link is severed and allows light to escape. Alternatively, all input ports except for a single remaining port can be disconnected from their respective amplifiers, and the processing device can proceed to learn the connectivity of the remaining input port. Specifically, a pilot signal can be inserted into the optical path of each amplifier sequentially, and an operator then looks for the presence of the pilot signal at the remaining input port. When the pilot signal is detected at the remaining input port in response to stimulating a given one of the amplifiers, the operator concludes that there is a connection between that amplifier and the remaining input port. This process is repeated for the next input port, and so on. As can be appreciated, this technique is time consuming and, furthermore, requires traffic flow to be interrupted during connection discovery.
Clearly, there is a need to provide a faster approach to connection discovery that does not require the interruption of traffic flow during the discovery process.
The present invention capitalizes on the fact that many optical amplifiers provide optical amplification using a xe2x80x9cpumpedxe2x80x9d laser source. In different embodiments, this may be achieved by excitation of a rare earth element (e.g., erbium) or, in the case of stimulated Raman scattering, by injecting energy in the form of light into the fiber that carries the signal to be amplified. Regardless of the physical phenomena involved in amplification, control information is embedded in the signal passing through an optical amplifier by varying the power level of that amplifier""s pumped laser source.
Connection discovery for a given optical port can then be performed by detecting variations in the optical signal present on that given port and then attempting to match these with the variations assigned to each of the optical amplifiers. If a match is found, then the optical amplifier connected to the given port can be identified. As a result, the need to physically handle the fiber in order to effect connection discovery is eliminated, rendering the process faster, safer and more reliable. Also, the present invention advantageously allows a connection discovery function to be invoked from a remote location.
Therefore, the invention may be summarized according to a first broad aspect as a method of discovering the existence of connections between at least one optical amplifier and at least one port, each optical amplifier being capable of optically amplifying an incoming traffic signal as a function of an intensity of an associated energy signal received from an energy source. The method includes varying the energy signal associated with each optical amplifier in accordance with a respective control signal and receiving an optical signal at each port in a subset of the at least one port. For each port in the subset, the method includes detecting each control signal present in the optical signal received at the port, each such control signal being a detected control signal for the port. Finally, for each port in the subset, the method includes determining the identity of each optical amplifier connected to the port on the basis of each detected control signal for the port and on the basis of the identity of the optical amplifier respectively associated with each detected control signal for the port.
According to a second broad aspect, the invention may be summarized as a connection discovery system for discovering the existence of connections between at least one optical amplifier and at least one port, each optical amplifier being capable of optically amplifying an incoming traffic signal as a function of an associated energy signal received from an energy source and being varied in accordance with a respective control signal. The system includes a receiver unit operable to receive an optical signal at each port in a subset of the at least one port. The system also includes a detection unit operable to detect, for each port in the subset, each control signal present in the optical signal received at the port, each such control signal being a detected control signal for the port.
Moreover, the system includes a controller operable to determine, for each port in the subset, the identity of each optical amplifier connected to the port on the basis of each detected control signal for the port and on the basis of the identity of the optical amplifier respectively associated with each detected control signal for the port.
The invention may be summarized according to a third broad aspect as a network element, including at least one optical amplifier capable of optically amplifying an incoming traffic signal as a function of an associated energy signal and at least one energy source. Each energy source is connected to a respective one of the at least one optical amplifier and is capable of generating the energy signal for the respective optical amplifier, each energy signal being variable in accordance with a respective control signal. The network element further contains a connection discovery system as described above.
According to a fourth broad aspect, the present invention may be summarized as a method of discovering the existence of connections between devices in an optical system. Each device is connected to respective input ports of a connection discovery system. Among the devices is included at least one optical amplifier capable of optically amplifying an incoming traffic signal as a function of an intensity of an associated energy signal received from an energy source. The method includes varying the energy signal associated with each optical amplifier in accordance with a respective control signal, receiving an optical signal at each port of the connection discovery system and searching for the presence of a control signal present in the optical signal received at each port. If the same control signal is present in the optical signal received at each port in a particular set of ports, it is concluded that the devices connected to the particular set of ports are connected to one another.
These and other aspects and features of the present invention will now become apparent to those of ordinary skill in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying drawings.